The clinical utilization of a pointed hollow needle mounted inside a flexible catheter tube is well known in the medical art for the introduction of a catheter. In such a medical instrument, the catheter tube is positioned tightly around the needle in such a way as to allow the needle to slide and telescope along the length of the catheter tube. Before use, the tip of the needle is protruding slightly through the opening of the catheter tube to allow facile penetration through the skin. Upon puncturing of the skin and introduction of the needle, the distal end of the catheter tube is simultaneously brought into place inside the desired target body cavity of the patient, such as the inside of a blood vessel, for example a vein. The needle has then done its duty in assisting the introduction of the catheter and is withdrawn by being pulled backwards through the catheter. Upon release of the needle, the catheter is set in its intended working mode extending over a lengthier period of time and including, for example, periodical administration or infusion of fluids or medications in liquid form, the collection of blood samples and the like.
An unprotected released needle constitutes, however, a serious health hazard due to the fact that it may be contaminated with e.g. infectious agents originating from the patient's blood or other body fluids, in combination with the needle tip's inherent ability to easily penetrate skin. Hence, the medical personnel who are handling the released needle may acquire the corresponding disease, e.g. HIV or hepatitis, if by accident contacting it with their skin. In order to circumvent or alleviate the health hazards associated with such a released needle amongst other things, there has been much effort devoted to the development of various kinds of needle tip protectors with a special focus on automatic variants of a type which may be referred to as being “foolproof”.
U.S. Pat. No. 6,616,630 B1, by B. Braun Melsungen A. G. discloses a safety IV catheter comprising a resilient spring clip normally positioned in the catheter hub. The needle of the safety IV catheter passes through a hole in the spring clip which allows axial movement of the needle. When the needle is in the forward position, i.e. when the safety IV catheter is ready for use, the presence of the needle forces parts of the spring clip into a position where these parts locks to the inside of the catheter hub, whereby movement of the spring clip relative the catheter hub is prevented. As the needle is withdrawn to a point where the tip passes these parts, the spring clip snaps into a position in which it is blocking access to the to the tip of the needle. Simultaneously, the part of the spring clip that previously locked to the inside of the catheter hub snap out of this position, whereby movement of the spring clip relative the catheter hub may occur. As the needle is further withdrawn, means are provided, e.g. a slot or a crimp on the needle, to lock the spring clip to the needle, whereby the spring clip is ejected from the catheter hub together with, and positioned on, the needle.
For various reasons, including e.g. practical, economical and technical reasons, the above described spring clips, and similar marketed variants, are today by necessity made of metal and catheter hubs of a plastic material. Disadvantages of the combination of these materials in this application include the release of e.g. microscopic plastic chips and metallic particles by the scraping of the metal spring clip against the inside of the plastic catheter hub when the former is ejected from the latter upon withdrawal of the needle. These chips and particles may easily be flushed into the bloodstream of a patient upon normal use of the corresponding catheter, and thus represent a serious health hazard to the same.
Spring clips, like the type described above and similar marketed variants, and needles, are today both by necessity made of metal. One disadvantage of the spring clip of this and similar safety IV catheters is the scraping vibration generated as the needle slides through and on the spring clip as it is withdrawn. This scraping vibration, which is due to metal sliding over metal and which can be clearly heard and felt, is highly uncomfortable and worrisome to the patient, who already is in an uncomfortable and exposed situation and may be very anxious.
Furthermore, spring clips, like the type disclosed above, provide poor protection per se against drops of blood or body fluid that may move outwards from the interior of the catheter hub as the needle is removed. Such drops may, for example, spread infectious diseases.
GB2451153(A) by Poly Medicure Ltd discloses a needle safety device for an intravenous catheter apparatus that includes a base capable of receiving a needle between opposing jaws attached to the base and capable of being influenced by the needle. The jaws have a link connecting the jaws arranged a distance from the base. The jaws may move between an expanded position in which they interact with an obstruction within a wing housing of the intravenous catheter apparatus. The jaws permit relative movement of the needle with the base when expanded, close around a needle tip as it passes the jaws, and prevent relative movement of the needle with the base when the jaws are collapsed.
However, when collapsed, each and one of the jaws do not extend further than maximally to the center axis of the needle. The particular jaw, onto which the tip of the needle is pointing, may thus relatively easy reveal the needle tip if it happens to be bent. In addition, the jaws need to be forced together with a link. This link represents an additional part of the device, which increases cost and complicates production of the same.
EP657184(A1) by the BOC Group plc discloses a medical device, for example, an IV cannula or a syringe which has a hollow needle with a sharp distal end for piercing the skin of a patient and includes means for protecting the sharp end of the needle after use to minimize the possibility of accidental needle stick. The means includes a rod mounted for movement through the needle between a needle end protection position and a retracted position within the hollow needle, and means for maintaining the rod towards the needle end protection position.
However, since the needle tip is not protected in the protection position there is a risk that the needle may cause dermal wounds if the needle engages the skin close to parallel or at a minor angle towards the skin.
Hence, an improved device for automatic shielding of the needle tip of a needle after its employment for introduction of a catheter tube is desired.